125cc no powerband help!

[Yamyzfrrider]

I just rebuilt my old 1988 yz 125cc bottom and top end. Everything is running, but I don't think the bike is running properly. :bang: What happend was about 7 yrs ago I blew the bottom end bearing and the bike has been sitting since until about 1 month ago. I replaced the rod and top end with a weisco piston and hot rod kit. I've been riding the bike a lot and it runs good but It has no power band whatsoever. I know my bike has a power band because before I blew the bottom end it hauled butt, but now it seems really slow. Could this be a carboretor problem or a valve problem? Any help would be great. Thanks.

 

[elf]

Explain what you mean by no (power band), Where does it run good? and what is missing ? Top end power? low end?

 

[KTA]

I'd bet its your carbs. After sitting for 7 years (or even a few months) they tend to get gummed up. I bet if you gave your carbs a good cleaning, and possibly a rebuild kit (new float, gaskets, etc) it would get it's groove back.

 

[Yamyzfrrider]

Explain what you mean by no (power band), Where does it run good? and what is missing ? Top end power? low end?

It just feels like there is no top end power at all. Low end seems to be fine.

 

[elf]

If your carb is clean, then your problem is with the power valve. Its not opening all the way or not at all. I had the same problem with a 89 yz 125. Check to make sure every thing is hooked up correctly.

 

[hrc125rider]

im going along wit that the accuater on the power valve is seized b/c i had the same problem with my 88cr125

 

[Yamyzfrrider]

I finally fixed the problem. I took off the exhaust and got a flash light and looked in the exhaust port and found out that the valve was positioned 180 degrees out of place. I took off the push rod and rotated the valve 180 degrees back to normal and boy does my bike haul butt now. Thanks guys for the help. I appreciated it.